This is the VOA Special English Health Report.

C.O.P.D., chronic obstructive pulmonary disease, blocks airflow through the lungs. It makes breathing difficult. The leading cause is cigarette smoking. Experts at the National Institutes of Health in the United States say the damage to the lungs cannot be repaired and there is no cure.

Dawn DeMeo is an assistant professor at Harvard Medical School in Boston, Massachusetts. 

DAWN DeMEO: "By two thousand and twenty, C.O.P.D. will likely be the third leading cause of death across the world."

C.O.P.D. is a new name for emphysema and chronic bronchitis. These are the two most common forms of the disease. Many people with C.O.P.D. have both of them. And Doctor DeMeo says more women than men now die from the disease.

She is the lead author of a study by a team from Harvard's Brigham and Women's Hospital and the University of Bergen in Norway. The new study adds to findings that women may be more at risk than men for the damaging effects of smoking. 

The team examined results from a Norwegian study of nine hundred fifty-four people with C.O.P.D. Inga-Cecilie Soerheim co-authored the team's findings. Doctor Soerheim says they show that women suffered the same severity of C.O.P.D. as men. But, by comparison, the female smokers were younger and had smoked a lot less. 

The team also looked at two groups among the people in the study. These were people under the age of sixty and those who had smoked for less than twenty years. In both cases, women had more severe C.O.P.D. and a greater loss of lung function than men.

Doctor DeMeo says some of the people in the study did not smoke much but still developed severe lung disease.

DAWN DeMEO: "Many people underestimate the health risks of their own cigarette consumption, thinking that a few cigarettes here and there, a few cigarettes every day, are harmless. But clearly there is no such thing as a safe level of cigarette smoke exposure. And our findings suggest that this is particularly true for women." 

The study was presented last month to the American Thoracic Society.

Doctor Soerheim says there are several possible explanations why women may be more at risk from the effects of cigarette smoke than men. Women have smaller airways, she says, so each cigarette may do more harm. Also, there are differences between males and females in the way the body processes cigarette smoke. And she says genes and hormones could also play an important part.

And that's the VOA Special English Health Report, written by June Simms. You can comment on our reports, and read what other people are saying, at voaspecialenglish.com. I'm Steve Ember.